The present invention is directed to a device suitable for providing a user's pelvic and upper body portions with dynamic continuous passive motion. Specifically, the present invention is directed to a device suitable for use as a seat wherein operation of the device with a user seated thereon provides undulatory movement of the seat for simulating the natural biomechanics of the spinal column, musculoskeletal system, soft tissues and fluid movement of the body.
Passive motion, by definition, refers to any movement of an articulation, body part or tissue that is produced by some external force. The source of the motion is any force other than the neuromuscular units that would normally be powering the motion under voluntary control. Passive motion may be placed on a spectrum extending from almost complete immobilization to continuous, uninterrupted movement.
Clinical observations reveal deleterious effects of prolonged immobilization of joints and tissues in patients. Clinical observations also have shown the beneficial local effects of early active motion as opposed to prolonged immobilization of diseased and injured body parts. Also, motion of the spine and extremities of paraplegic or quadriplegic patients reduce their susceptibility to necrosis, or pressure sores, resulting from prolonged immobilization. Continuous passive motion has been demonstrated to be extremely helpful for those with spinal injuries. Additionally, continuous passive motion has been demonstrated to be helpful to otherwise healthy individuals subject to prolonged immobilization such as office workers, motor vehicle operators and passengers, jurors, or the like.
It is well known that the biomechanics of the spine put the body into six degrees of motion (flexion, extension--right and left, rotation--right and left, lateral bendings, as well as long-axis distraction and compression or load/unload cycles). During the normal gate cycle, the spine is in a lordotic position wherein the portions of the spine receive a circumductive load and unload force. This load and unload cycle occurs each time a step is taken as gravity forces the body downward. This cycle, or pumping action creating a load/unload cycle, has with it a slight rotational component as the arms swing and the legs step alternately.
Those confined to a wheelchair, suffering from spinal injuries, or otherwise healthy individuals subjected to prolonged immobilization are not able to put the spinal column in active motion, or otherwise, to promote the benefits of passive motion and the circulation of blood through the spine/pelvic region and legs. For the foregoing reasons, there is a need for a device to simulate the natural undulatory movement and the redistributing weight bearing structures of the spine through continuous passive motion.
One such device is shown in U.S. Pat. No. 5,113,851 to Gamba, which shows a chair that automatically and continuously tilts and oscillates in such a way as to change the position of the body of the person seated on the chair. It has been determined, however, that chairs such as that shown in the Gamba suffer from disadvantages. For example, the entire seat of the Gamba chair is put in motion, which translates into movement of the legs, hips, and spine, etc. It has been determined that more effective pertinent exercise is provided when the spine is isolated. Thus, moving the legs, etc., is an inefficient use of power. General lower body motion of the type described above, in addition to being inefficient, can also create discomfort in many individuals.